In an aircraft gas turbine (jet) engine, air is drawn into the front of the engine, compressed by a shaft-mounted compressor, and mixed with fuel. The mixture is combusted, and the resulting hot combustion gas is passed through a turbine mounted on the same shaft. The flow of gas turns the turbine by contacting an airfoil portion of the turbine blade, which turns the shaft and provides power to the compressor. The hot exhaust gases flow from the back of the engine, driving it and the aircraft forward. There may additionally be a bypass fan that forces air around the center core of the engine, driven by a shaft extending from the turbine section.
The compressor, the turbine, and the bypass fan have a similar construction. They each have a rotor assembly included in a rotor disk and a set of blades extending radially outwardly from the rotor disk. The compressor, the turbine, and the bypass fan share this basic configuration. However, the materials of construction of the rotor disks and the blades, as well as the shapes and sizes of the rotor disks and the blades, vary in these different sections of the gas turbine engine. The blades may be integral with and metallurgically bonded to the disk, forming a BLISK (“bladed disk”, also sometimes known as an “integrally bonded rotor” or IBR), or they may be mechanically attached to the disk.
During manufacture or service, one (or more) of the blades of the BLISK may be damaged, as for example, by the impact of particles entrained in the gas flow that impinges on the blade. If the damage is nicks, dents, or local loss of material, the blade must be repaired. In the repair, the damaged area has new material deposited onto it. The BLISK is then heat treated to relieve residual stresses. However, the heat treatment exposure of the entire BLISK can reduce the properties of the other areas of the BLISK and is not desirable.
What is needed is a heat-treatment apparatus that can be used to heat treat a portion of a weld-repaired BLISK airfoil without exposing the entire BLISK to the heat treatment. The present invention fulfills this need, and further provides related advantages.